Protractor



Jan. 23, 1934. E. w. sANDr-:LL

PROTRACTOR Filed April 29, 1932 1l INVENTOR.

.EV` I E EDWARDN. SHHDELL l 7 l 5 ATTORNEYS.

,Patented Jan. 23, 1934 NETE@ STATES PATENT OFFICE 1 Claim.

This invention relates to improvements in protractors.

The principal object of the invention is to provide a protractor which may be used for drawing purposes with T-square angles or without the same.

A further object of the invention is to produce a protractor which has indicia formed on the underside thereof for accurate measurement.

A further object is to produce a device wherein there are no extending arms which may be readily damaged.

Another object is to produce a device which is economical to manufacture and one which is neat iin appearance.

An additional object is to produce a device which will have a iiat bearing surface, and therefore will contact the drawing paper throughout its entire surface.

Tl A still further object is to provide means whereby an arm of the protractor may be located at various positions for the drawing of angular lines. Other objects and advantages will be apparent during the course of the following description. In the accompanying drawing forming a part of this specification and in which like numerals are employed to designate like parts throughout the same,

Fig. 1 is a top plan view of my device, Fig. 2 is an enlarged cross sectional View taken on the line 2 2 of Fig. 1,

Fig. 3 is an enlarged top plan View of the protractor arm, and

Fig. l is a cross sectional view taken on the .line 4 4 of Fig. 3.

In the art of drafting, it is often necessary to employ means for determining and drawing angles of a definite number of degrees. Applicant has therefore devised a simple tool with which this may be accomplished.

In the accompanying drawing wherein for -the purpose of illustration is shown a preferred embodiment of my invention,` the numerals 5 and 6 refer to right angle legs joining each other at an '..angle of 90 and the numeral 7 designates a quadrant extending between the free ends of the legs 5 and 6. The legs 5 and 6 and also the quadrant have indicia formed thereon. These indicia are preferably engraved or otherwise placed upon the bottom or undersurface of the tool so that the division lines will be in close proximity to the surface of the drawing. It is of course understood that the device is preferably made of a transparent material so that the indicia may be viewed therethrough.

A rounded offset pivotal portion 8 is carried upon the device and formed integral therewith at a point adjacent the junction of the legs 5 and 6. The undersurface of the quadrant is undercut to provide a groove 9, extending along the inner edge thereof and the purpose of which will be later seen. An arm 11 has one end pivoted as at l2 to the pivot portion 8 and its opposite end cverlies the quadrant for slidable movement thereon and is reduced at its sides in curved formation to provide a point 13 that has extending therefrom a center line 14 arranged upon the undersurface of the arm so as to be in as close proximity to the indicia on the quadrant, whereby the point and line cooperate therewith, as will be apparent upon inspection of Figure 2. This arm also has indicia formed upon its undersurface in a manner previously described for the legs 5 and 6 and the quadrant 7. This arm 11 has secured tc its undersurface, a backing strip 16 which has one end shaped as shown at 17 so as to conform to the outline cf the pivot portion 8 and has its opposite end provided with a recess 18 to receive an elongated head 19, of a bolt 21 upon which Va thumb screw 22 is threadedly mounted. This head 19 has a portion thereof underlying the undercut 9 of the quadrant 7, the result being that should a person wish to draw a line having an angle of inclination from a horizontal of 15, the arm 11 will be moved to the position of Figure 1 until the line 14 overlies the line representing 15 on the quadrant, after which the nut 22 is tightened binding the arm to the quadrant as best illustrated in Fig. 2.

It is, of course, understood that when the arm 11 is parallel to either of the legs 5 or 6, then the same will be at an angle of 90 to the leg at the opposite end of the quadrant from the arm.

It is to be understood that the form of my in. vention herewith shown and described is to be taken as a preferred example of the same and that various changes relative to the material, size, shape and arrangement of parts may be resorted to without departing from the spirit of the invention or the scope of the subjoined claim.

Having thus described my invention, I claim:-

A measuring instrument comprising a pair of indicia bearing legs connected together at one end and disposed at right angles with respect to each other, an indicia bearing quadrant extendn ing between and connected to the other ends, said quadrant having a groove on its underside and extending along its inner edge, a yrounded offset portion extending inwardly from the juncture of the legs with each other, an indicia bearing arm portion and its opposite end having a, recess therein arranged to register with the groove, a bolt having a head arranged in the recess and extending into the groove for slidable movement in the latten-and means on the bolt for cooperation with the head for securing the arm in adjusted positions with respect to the quadrant.

' EDWARD W. SANDELL. 

